Myasthenia Gravis

Definition

Myasthenia gravis
(MG) is an autoimmune disease. It affects the connection between the nerves and skeletal muscles.
This can cause progressive muscle weakness.

Causes

The root cause of MG is unknown. It occurs when the body’s immune system attacks receptors in muscle. Normally, these receptors respond to the chemical acetylcholine (ACh). This chemical allows nerve signals to prompt the muscles to move. When the immune system prevents these receptors from working well, the muscles cannot respond to nerve signals.

The thymus is thought to play a role in some cases of MG. The thymus is an organ behind the breastbone. Immune proteins called antibodies are produced there. It is these antibodies that may target the ACh receptors. It is still not clear why the thymus begins to produce these.

Infants of mothers with MG are more likely to develop a temporary form. It is called neonatal MG. The mother’s abnormal antibodies enter the baby’s bloodstream. When the baby is born, there may be muscle weakness. The abnormal antibodies are often cleared from the baby in about two months. This will end the baby’s symptoms.

Risk Factors

MG is most common in women less than 40 years old and in men over 60 years old.

Symptoms

Symptoms may grow more severe over time. MG may cause the following:

Muscle weakness that increases with muscle use/exercise, and improves after resting those muscles

Drooping eyelids

Double and/or blurred vision

Difficulty swallowing

Difficulty speaking

Difficulty walking

Weakness of the hand muscles

Difficulty breathing

Diagnosis

Your doctor will ask about your symptoms and medical history. A physical exam will be done. You may need to see a neurologist. This type of doctor is an expert in diseases of the nervous system. Tests may include:

Medications

Plasmapheresis

Plasmapheresis
is a procedure that cleans the blood of the abnormal antibodies. This process may need to be repeated at certain intervals.

Surgery

Thymectomy
is a surgical procedure to remove the thymus gland. Surgery may improve symptoms or bring remission in some people.

Mechanical Ventilation

This may only be needed if breathing is severely impaired. This can happen during an episode of myasthenic crisis.

Physical and Occupational Therapy

Therapy does not generally alter the course of the disease. It may be needed to help the patient cope with changes in muscle strength. It may also help with learning alternative ways to approach daily activities.

Avoiding Medications That May Worsen Symptoms

Avoid medications that may worsen MG. Some examples include:

Beta-blockers

Certain antibiotics

Certain medications used to treat psychiatric conditions

Prevention

There are no current guidelines to prevent MG.

Revision Information

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.